Precise measurement of the angular position of a rotating body is essential in many applications. For example, in the field of medical imaging, computed tomography (CT) scanning equipment requires knowledge of the angular position of the CT gantry during operation. Likewise, devices that employ rotating gimbals to orient equipment such as cameras and radar often need to know angular position in real time.
While conventional devices such as Michelson interferometers can be employed to measure the angular position of a rotating body, practical limitations prevent such solutions from working at higher speeds. For example, a gantry having a diameter of about 2 meters rotating at about 5 revolutions per second experiences outer diameter speeds of about 5 meters/second, which is too fast for conventional interferometric techniques relying on commercially available components. A need remains for high-accuracy techniques for measuring angular position that are capable of operating at a greater range of rotation rates.